The brother of a female police officer who collapsed and died chasing phone thieves today paid an emotional tribute to her sister who he said "loved putting criminals away".

Speaking for the first time since Detective Constable Adele Cashman died four months ago, her brother Adam said the pain of her death “would never go away”.

But the 29-year-old - whose sister had been on course to join the Met’s gun crime Trident unit - said his family have been consoled by a deluge of messages including a letter from London Mayor Boris Johnson.

And he revealed he and some of Dc Cashman’s closest friends are to run next month’s London Marathon in her honour - and raise thousands of pounds for a children’s charity that was close to her heart.

Dc Cashman, originally from Bristol, collapsed and died last November while chasing phone thieves in Belsize Park, north London.

She had been chasing two boys who had allegedly snatched a mobile phone from a 59-year-old woman in Haverstock Hill.

An inquest yesterday found the fit young detective was killed by “fatal cardiac dysrhythmia” or an abnormal heart rate.

The officer, whose nickname was Del Boy, had planned to run the 2013 Edinburgh marathon for the Bristol-based charity Cots For Tots.

“I had a daughter in January last year and while she loved her career I think she was also looking forward to having children of her own,” said Mr Cashman, who works for his family’s property business in Bristol.

“She had tried to get in to the London Marathon several times in the past but never managed it. So she decided to do the Edinburgh marathon.

“She was always trying to get me to run with her her. I kept saying ‘no, I’m not doing that, I hate running.’

“I played rugby and was reasonably fit but I’ve never been a runner.

“But a few days after she died I asked her sergeant if he could get me a place in the marathon. It was something she always wanted to do. I just wanted to do it for her.”

Her sergeant managed to organise four places in the 26-mile run so Mr Cashman is being joined by three close friends, including Adele’s closest colleague in the Met, Claire Hart.

Other friends will be running the Paris marathon next month and the Edinburgh half-marathon in May in a bid to raise more than £10,000 in total for the children’s charity.

After her death, the Cashman family were tested for any heart abnormalities and have been given the all-clear.

Her brother said: “Adele was fit and healthy. That’s why it was such a shock. It was just a sudden failure of a normal heart.

“She was a family girl who loved to spend time with her friends. She also loved travelling but was very career-driven. She had just applied for Trident which was going to be quite a big step.

“She loved putting criminals away.”

He added: “Time doesn’t heal, you just have to deal with it. But we are raising money for a great cause. That’s what Adele would have wanted.”